1922 - 'Marconiphone' department formed by Marconi Company to manufacture, design and sell domestic radios;

1923 - Marconiphone Co Ltd formed as subsiduary of Marconi Company;

1929 - Marconiphone sold to His Master's Voice (HMV) (whose's parent company was the Gramophone Company) along with right to use 'Marconiphone' trademark;

1931 - the Gramophone Company became EMI, who continued making domestic radio rececivers under Marconiphone trademark until 1956; note that no receivers with Marconiphone trademark after 1929 have any connection with Marconi Company.